1. Field of the Invention
The present invention relates to a rocker arm which is used in an engine valve opening and closing mechanism.
2. Description of the Related Arts
A valve opening and closing mechanism used in a reciprocal engine of a vehicle or the like is constructed so as to execute suction and exhaust of air in the engine by opening and closing an engine valve by rocking of a rocker arm with receiving rotation of a cam. For example, in an overhead cam (OHC) type engine, a rocker arm supports a roller via a supporting pin between a pair of side wall portions. This rocker arm rocks so as to execute opening and closing of the engine valve while rotating the roller with rotation of the cam.
The engine has a rocking support member such as a pivot, a lash adjuster or the like for forming a rocking support point of the rocker arm. An engaging portion formed at an end of the rocker arm engages with the rocking support member. The engaging portion of the rocker arm is for example in shape of a spherical concave portion depressed toward the opposite direction to the pivot so as to engage with a spherical protruding portion of the pivot, as disclosed in the patent document 1. The engaging portion of the rocker arm is for example in shape of a convex spherical shape projecting toward the direction to the pivot so as to engage with the spherical concave portion formed at the end portion of the pivot as disclosed in the patent document 2.
However, in the above-described conventional rocker arm, the engaging portion engaging with the rocking support member is formed with projecting toward only one direction from a board surface portion connecting a pair of side wall portions. Thus, positional relationship between the rocking support member and the engaging portion in the rocking direction (direction the rocker arm rocks which is vertical or oblique to vertical direction) is restricted.
Furthermore, especially in the case which the pair of side wall portions standing toward the rocking support member is formed to be extended to both side portions of the engaging portion, the pair of side wall portions of the engaging portion might interfere with peripheral members around the rocker arm such as the rocking support member or the like. Therefore, in this case, it is difficult to improve rigidity of the engaging portion of the rocker arm.
Patent document 1: JP2003-138914 Unexamined Patent Publication (Kokai)
Patent document 2: JP2002-161717 Unexamined Patent Publication (Kokai)